Electrostatic discharge (ESD) protection circuit and method of operating the same

ABSTRACT

An electrostatic discharge (ESD) protection circuit includes a first diode, a second diode and an ESD clamp circuit. The first diode is in a semiconductor wafer, and is coupled to an input output (IO) pad. The second diode is in the semiconductor wafer, and is coupled to the first diode and the TO pad. The ESD clamp circuit is in the semiconductor wafer, and is coupled to the first diode and the second diode. The ESD clamp circuit includes a first signal tap region in the semiconductor wafer. The first signal tap region is coupled to a first voltage supply. The first diode is coupled to and configured to share the first signal tap region with the ESD clamp circuit.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No.63/002,562, filed Mar. 31, 2020, which is incorporated herein byreference in its entirety.

BACKGROUND

The recent trend in miniaturizing integrated circuits (ICs) has resultedin smaller devices which consume less power, yet provide morefunctionality at higher speeds than before. The miniaturization processhas also increased the devices' susceptibility to electrostaticdischarge (ESD) events due to various factors, such as thinnerdielectric thicknesses and associated lowered dielectric breakdownvoltages. ESD is one of the causes of electronic circuit damage and isalso one of the considerations in semiconductor advanced technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic block diagram of an integrated circuit, inaccordance with some embodiments.

FIG. 2 is a schematic block diagram of an integrated circuit, inaccordance with some embodiments.

FIG. 3A is a cross-sectional view of an integrated circuit, inaccordance with some embodiments.

FIG. 3B is a cross-sectional view of an integrated circuit, inaccordance with some embodiments.

FIG. 4 is a cross-sectional view of an integrated circuit, in accordancewith some embodiments.

FIG. 5 is a flowchart of a method of operating an ESD circuit, inaccordance with some embodiments.

FIG. 6 is a flowchart of a method of manufacturing an ESD circuit, inaccordance with some embodiments.

FIGS. 7A-7E are cross-sectional views of an integrated circuit, inaccordance with one or more embodiments.

DETAILED DESCRIPTION

The following disclosure provides different embodiments, or examples,for implementing features of the provided subject matter. Specificexamples of components, materials, values, steps, arrangements, or thelike, are described below to simplify the present disclosure. These are,of course, merely examples and are not limiting. Other components,materials, values, steps, arrangements, or the like, are contemplated.For example, the formation of a first feature over or on a secondfeature in the description that follows may include embodiments in whichthe first and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formed betweenthe first and second features, such that the first and second featuresmay not be in direct contact. In addition, the present disclosure mayrepeat reference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In some embodiments, an ESD protection circuit includes a first diode, asecond diode and an ESD clamp circuit. The first diode is in asemiconductor wafer, and is coupled to an input output (TO) pad. Thesecond diode is in the semiconductor wafer, and is coupled to the firstdiode and the IO pad. The ESD clamp circuit is in the semiconductorwafer, and is coupled to the first diode and the second diode. The ESDclamp circuit includes a first signal tap region and a second signal tapregion in the semiconductor wafer. The first signal tap region iscoupled to a first voltage supply. The second signal tap region iscoupled to a second voltage supply different from the first voltagesupply.

The first diode is coupled to and configured to share the first signaltap region with the ESD clamp circuit. The second diode is coupled toand configured to share the second signal tap region with the ESD clampcircuit. In some embodiments, by the first diode sharing the firstsignal tap region with the ESD clamp circuit, and by the second diodesharing the second signal tap region with the ESD clamp circuit, the ESDprotection circuit of the present disclosure occupies less area thanother approaches.

In some embodiments, by the first diode sharing the first signal tapregion with the ESD clamp circuit, and by the second diode sharing thesecond signal tap region with the ESD clamp circuit, the ESD protectioncircuit of the present disclosure has less signal taps than otherapproaches resulting in the ESD protection circuit of the presentdisclosure having less resistance than other approaches. In someembodiments, by having less resistance than other approaches, the ESDprotection circuit of the present disclosure has a lower clampingvoltage and is faster in operation than other approaches.

FIG. 1 is a schematic block diagram of an integrated circuit 100, inaccordance with some embodiments.

Integrated circuit 100 comprises an internal circuit 102, a voltagesupply node 104, a reference voltage supply node 106, an input/output(IO) pad 108, a diode D1, a diode D2, an IO circuit 110 and an ESD clampcircuit 120. In some embodiments, at least integrated circuit 100, 200(FIG. 2 ) or 300A-300B (FIGS. 3A-3B) is incorporated on a singleintegrated circuit (IC), or on a single semiconductor substrate. In someembodiments, at least integrated circuit 100, 200 (FIG. 2 ) or 300A-300B(FIGS. 3A-3B) includes one or more ICs incorporated on one or moresingle semiconductor substrates.

Internal circuit 102 is coupled to the IO circuit 110. In someembodiments, internal circuit 102 is further coupled to IO pad 108,diode D1 and diode D2. Internal circuit 102 is configured to receive anIO signal from IO pad 108 through IO circuit 110. In some embodiments,internal circuit 102 is coupled to voltage supply node 104 (e.g. VDD)and reference voltage supply node 106 (e.g., VSS). In some embodiments,internal circuit 102 is configured to receive a supply voltage VDD fromvoltage supply node 104 (e.g. VDD), and a reference supply voltage VSSfrom reference voltage supply node 106 (e.g., VSS).

Internal circuit 102 includes circuitry configured to generate orprocess the IO signal received by or output to IO pad 108. In someembodiments, internal circuit 102 comprises core circuitry configured tooperate at a voltage lower than supply voltage VDD of voltage supplynode 104. In some embodiments, internal circuit 102 includes at leastone n-type or p-type transistor device. In some embodiments, internalcircuit 102 includes at least a logic gate cell. In some embodiments, alogic gate cell includes an AND, OR, NAND, NOR, XOR, INV, AND-OR-Invert(AOI), OR-AND-Invert (OAI), MUX, Flip-flop, BUFF, Latch, delay, or clockcells. In some embodiments, internal circuit 102 includes at least amemory cell. In some embodiments, the memory cell includes a staticrandom access memory (SRAM), a dynamic RAM (DRAM), a resistive RAM(RRAM), a magnetoresistive RAM (MRAM) or read only memory (ROM). In someembodiments, internal circuit 102 includes one or more active or passiveelements. Examples of active elements include, but are not limited to,transistors and diodes. Examples of transistors include, but are notlimited to, metal oxide semiconductor field effect transistors (MOSFET),complementary metal oxide semiconductor (CMOS) transistors, bipolarjunction transistors (BJT), high voltage transistors, high frequencytransistors, p-channel and/or n-channel field effect transistors(PFETs/NFETs), FinFETs, and planar MOS transistors with raisedsource/drain. Examples of passive elements include, but are not limitedto, capacitors, inductors, fuses, and resistors.

Voltage supply node 104 is coupled to diode D1 and ESD clamp circuit 120at node Nd1. Reference voltage supply node 106 is coupled to diode D2and ESD clamp circuit 120 at node Nd2. Voltage supply node 104 isconfigured to receive supply voltage VDD for normal operation ofinternal circuit 102. Similarly, reference voltage supply node 106 isconfigured to receive reference supply voltage VSS for normal operationof internal circuit 102. In some embodiments, at least voltage supplynode 104 is a voltage supply pad. In some embodiments, at leastreference voltage supply node 106 is a reference voltage supply pad. Insome embodiments, a pad is at least a conductive surface, a pin, a nodeor a bus. Voltage supply node 104 or reference voltage supply node 106is also referred to as a power supply voltage bus or rail. In theexample configuration in FIG. 1, 2 or 3A-3B, supply voltage VDD is apositive supply voltage, voltage supply node 104 is a positive powersupply voltage, reference supply voltage VSS is a ground supply voltage,and reference voltage supply node 106 is a ground voltage terminal.Other power supply arrangements are within the scope of the presentdisclosure.

IO pad 108 is coupled to IO circuit 110 by a node Nd3. IO pad 108 iscoupled to internal circuit 102 by IO circuit 110. In some embodiments,IO circuit 110 is not included in integrated circuit 100, and IO pad iscoupled to internal circuit 102 directly. IO pad 108 is configured toreceive IO signal from IO circuit 110 or configured to output IO signalto IO circuit 110. IO pad 108 is at least a pin that is coupled to IOcircuit 110 or internal circuit 102. In some embodiments, IO pad 108 isa node, a bus or a conductive surface that is coupled to IO circuit 110or internal circuit 102.

Diode D1 is coupled between voltage supply node 104 and IO pad 108.Diode D1 is coupled between node Nd1 and node Nd3. An anode of diode D1is coupled to node Nd3, IO circuit 110, IO pad 108 and a cathode ofdiode D2. A cathode of diode D1 is coupled to voltage supply node 104,ESD clamp circuit 120 and node Nd1. In some embodiments, the cathode ofdiode D1 is coupled to ESD clamp circuit 120 by node Nd1. In someembodiments, diode D1 is a pull-up diode or referred to as a p+ diode.For example, in these embodiments, the p+-diode is formed between ap-well region (e.g., well 322 of FIGS. 3A-3B) and an n-well region (notshown), and the n-well region is connected to VDD (See FIGS. 3A-3B). Insome embodiments, diode D1 is a vertical well diode. Other diode typesfor diode D1 are within the scope of the present disclosure.

Diode D2 is coupled between reference voltage supply node 106 and IO pad108. Diode D2 is coupled between node Nd3 and node Nd2. An anode ofdiode D2 is coupled to reference voltage supply node 106, ESD clampcircuit 120 and node Nd2. A cathode of diode D2 is coupled to node Nd3,IO circuit 110, IO pad 108 and the anode of diode D1. In someembodiments, diode D2 is a pull-down diode or referred to as an n+diode. For example, in these embodiments, the n+-diode is formed betweenan n-well region (e.g., well 332 of FIGS. 3A-3B) and a p-well (notshown), and the P-substrate is connected to ground or VSS. In someembodiments, diode D2 is a vertical well diode. Other diode types fordiode D2 are within the scope of the present disclosure.

Diodes D1 and D2 are configured to have a minimal impact on the normalbehavior (e.g., no ESD conditions or events) of internal circuit 102 orintegrated circuit 100. In some embodiments, an ESD event occurs when anESD voltage or current higher than a level of voltage or currentexpected during the normal operation of internal circuit 102 is appliedto at least voltage supply node 104, reference voltage supply node 106or IO pad 108.

When no ESD events occur, diodes D1 and D2 do not affect the operationof integrated circuit 100. During an ESD event, diode D1 is configuredto transfer voltage or current between voltage supply node 104 and IOpad 108 dependent upon whether diode D1 is forward biased or reversebiased, and the voltage levels of the voltage supply node 104 and IO pad108.

For example, during a Positive-to-VDD (PD) mode of ESD stress or event,diode D1 is forward biased and is configured to transfer voltage orcurrent from IO pad 108 to voltage supply node 104. In PD-mode, apositive ESD stress or ESD voltage (at least greater than supply voltageVDD) is applied to IO pad 108, while voltage supply node 104 (e.g., VDD)is ground and reference voltage supply node 106 (e.g., VSS) is floating.

For example, during a Negative-to-VDD (ND) mode of ESD stress or event,diode D1 is reverse biased and is configured to transfer voltage orcurrent from voltage supply node 104 to IO pad 108. In ND-mode, anegative ESD stress is received by IO pad 108, while the voltage supplynode 104 (e.g., VDD) is ground and reference voltage supply node 106(e.g., VSS) is floating.

During an ESD event, diode D2 is configured to transfer voltage orcurrent between reference voltage supply node 106 and IO pad 108dependent upon whether diode D2 is forward biased or reverse biased, andthe voltage levels of the reference voltage supply node 106 and IO pad108.

For example, during a Positive-to-VSS (PS) mode of ESD stress or event,diode D2 is reverse biased and is configured to transfer voltage orcurrent from IO pad 108 to reference voltage supply node 106. InPS-mode, a positive ESD stress or ESD voltage (at least greater thanreference supply voltage VSS) is applied to IO pad 108, while voltagesupply node 104 (e.g., VDD) is floating and reference voltage supplynode 106 (e.g., VSS) is ground.

For example, during a Negative-to-VSS (NS) mode of ESD stress or event,diode D2 is forward biased and is configured to transfer voltage orcurrent from reference voltage supply node 106 to IO pad 108. InNS-mode, a negative ESD stress is received by IO pad 108, while thevoltage supply node 104 (e.g., VDD) is floating and reference voltagesupply node 106 (e.g., VSS) is ground.

Other types of diodes, configurations and arrangements of at least diodeD1 or D2 are within the scope of the present disclosure.

IO circuit 110 is coupled to IO pad 108, internal circuit 102, diodes D1and D2 and node Nd3. IO circuit is coupled between node Nd3 and internalcircuit 102. In some embodiments, IO circuit is an IO buffer configuredto buffer signals sent to or from internal circuit 102. In someembodiments, IO circuit 110 includes at least the logic gate celldescribed above. Other types of circuits, configurations andarrangements of IO circuit 110 are within the scope of the presentdisclosure.

ESD clamp circuit 120 is coupled between voltage supply node 104 (e.g.supply voltage VDD) and reference voltage supply node 106 (e.g., VSS).ESD clamp circuit 120 is coupled between node Nd1 and node Nd2. ESDclamp circuit 120 is coupled to diode D1 by node Nd1. ESD clamp circuit120 is coupled to diode D2 by node Nd2.

When no ESD event occurs, ESD clamp circuit 120 is turned off. Forexample, when no ESD event occurs, ESD clamp circuit 120 is turned off,and is therefore a nonconductive device or circuit during the normaloperation of internal circuit 102. In other words, ESD clamp circuit 120is turned off or is non-conductive in the absence of an ESD event.

If an ESD event occurs, ESD clamp circuit 120 is configured to sense theESD event, and is configured to turn on and provide a current shunt pathbetween voltage supply node 104 (e.g. supply voltage VDD) or node Nd1and reference voltage supply node 106 (e.g., VSS) or node Nd2 to therebydischarge the ESD current. For example, when an ESD event occurs, thevoltage difference across the ESD clamp circuit 120 is equal to orgreater than a threshold voltage of ESD clamp circuit 120, and ESD clampcircuit 120 is turned on thereby conducting current between voltagesupply node 104 (e.g. VDD) and reference voltage supply node 106 (e.g.,VSS).

During an ESD event, ESD clamp circuit 120 is configured to turn on anddischarge an ESD current in a forward ESD direction (e.g., current I1 a)from the reference voltage supply node 106 (e.g., VSS) to the voltagesupply node 104 (e.g. VDD). Current I1 a is shown in FIG. 1 between nodeNd2 to node Nd1 for simplicity, but it is understood that current I1 ais from the reference voltage supply node 106 (e.g., VSS) to the voltagesupply node 104 (e.g. VDD).

During an ESD event, ESD clamp circuit 120 is configured to turn on anddischarge an ESD current in a reverse ESD direction (e.g., current I1 a)from the voltage supply node 104 (e.g. VDD) to the reference voltagesupply node 106 (e.g., VSS). Current I1 a is shown in FIG. 1 betweennode Nd1 to node Nd2 for simplicity, but it is understood that currentI1 a is from the voltage supply node 104 (e.g. VDD) to the referencevoltage supply node 106 (e.g., VSS).

During a positive ESD surge on reference voltage supply node 106, ESDclamp circuit 120 is configured to turn on and discharge the ESD currentI1 a in a forward ESD direction from the reference voltage supply node106 (e.g., VSS) to the voltage supply node 104 (e.g. VDD). In someembodiments, ESD clamp circuit 120 is configured to turn on, after a PSmode (described above) of ESD, and discharge the ESD current I1 in theforward ESD direction from node Nd3 to node Nd2, and from node Nd2 tothe voltage supply node 104 (e.g. VDD) by node Nd1.

During a positive ESD surge on voltage supply node 104, ESD clampcircuit 120 is configured to turn on and discharge the ESD current I1 ain a reverse ESD direction from voltage supply node 104 (e.g. VDD) toreference voltage supply node 106 (e.g., VSS). In some embodiments, ESDclamp circuit 120 is configured to turn on, after a PD mode (describedabove) of ESD, and discharge the ESD current I2 in the reverse ESDdirection from node Nd3 to node Nd1, and from node Nd1 to the referencevoltage supply node 106 (e.g., VSS) by node Nd2.

In some embodiments, ESD clamp circuit 120 is a transient clamp. Forexample, in some embodiments, ESD clamp circuit 120 is configured tohandle transient or ESD events, e.g., rapid changes in voltage and/orcurrent from the ESD event. During the transient or ESD, the ESD clampcircuit 120 is configured to turn on to provide a shunt path betweenvoltage supply node 104 (e.g. supply voltage VDD) and reference voltagesupply node 106 (e.g., VSS) before the ESD event can cause damage to oneor more elements within integrated circuit 100. In some embodiments, ESDclamp circuit 120 is configured to turn off slower than it turns on.

In some embodiments, ESD clamp circuit 120 is a static clamp. In someembodiments, static clamps are configured to provide a static orsteady-state voltage and current response. For example, static clampsare turned-on by a fixed voltage level.

In some embodiments, ESD clamp circuit 120 includes a large NMOStransistor configured to carry the ESD current without entering theavalanche breakdown region of the ESD clamp circuit 120. In someembodiments, ESD clamp circuit 120 is implemented without havingavalanching junctions inside ESD clamp circuit 120, and is also known asa “non-snapback protection scheme.”

Other types of clamp circuits, configurations and arrangements of ESDclamp circuit 120 are within the scope of the present disclosure.

Other configurations or quantities of circuits in integrated circuit 100are within the scope of the present disclosure.

FIG. 2 is a schematic block diagram of an integrated circuit 200, inaccordance with some embodiments.

Integrated circuit 200 is an embodiment of integrated circuit 100, andsimilar detailed description is therefore omitted. For example,integrated circuit 200 includes at least a portion of integrated circuit100 included as part of a substrate 202. While integrated circuit 200 ofFIG. 2 shows a portion of integrated circuit 100, it is understood thatintegrated circuit 200 can be modified to include each of the featuresof integrated circuit 100, and similar detailed description is thereforeomitted for brevity.

Components that are the same or similar to those in one or more of FIGS.1, 2, 3A-3B and 4 (shown below) are given the same reference numbers,and detailed description thereof is thus omitted.

Integrated circuit 200 includes voltage supply node 104, referencevoltage supply node 106, IO pad 108, diode D1, diode D2, substrate 202and a clamp circuit 220.

Integrated circuit 200 is a variation of integrated circuit 100 of FIG.1 , and similar detailed description is therefore omitted. In comparisonwith integrated circuit 100, ESD clamp circuit 220 replaces ESD clampcircuit 120 of FIG. 1 , and similar detailed description is thereforeomitted.

ESD clamp circuit 220 are formed on substrate 202. Substrate 202 extendsin a first direction X. Substrate 202 has a backside 203 and a frontside 205 opposite from the backside 203 in a second direction Y. In someembodiments, the second direction Y is different from the firstdirection X. In some embodiments, a bulk of substrate 202 has beenremoved during wafer thinning. In some embodiments, substrate 202 ispart of a super power rail (SPR) technology or process. In someembodiments, substrate 202 is a silicon on insulator (SOI) technology orprocess. In some embodiments, at least diode D1 or D2 is formed onsubstrate 202. Other types of substrate technology or processes forsubstrate 202 are within the scope of the present disclosure.

ESD clamp circuit 220 includes a signal tap 250 and a signal tap 252.

In some embodiments, at least signal tap 252 corresponds to a well tap.In some embodiments, a well tap is an electrically conductive lead thatcouples a well region (shown in FIG. 3A-3B) of substrate 202 to voltagesupply node 104 (e.g., supply voltage VDD). For example, in someembodiments, the well region includes a heavily doped n-region in ann-type well on a p-type substrate. In some embodiments, the heavilydoped n-region is coupled through the well tap to voltage supply node104 (e.g., supply voltage VDD) thereby setting the potential of then-type well to prevent leakage from adjacent source/drain regions intothe well.

In some embodiments, at least signal tap 250 corresponds to a substratetap. In some embodiments, a substrate tap is an electrically conductivelead that couples a region of substrate 202 to reference voltage supplynode 106 (e.g., reference supply voltage VSS). For example, in someembodiments, the region of substrate 202 includes a heavily dopedp-region which is formed in a p-type substrate. In some embodiments, theheavily doped p-region is coupled through the substrate tap to thereference voltage supply node 106 (e.g., reference supply voltage VSS)thereby setting the potential of the substrate 202 to prevent leakagefrom adjacent source/drain regions.

Through the use of signal taps 250 and 252 the resistance of substrate202 and undesirable positive feedback in integrated circuit 200 arereduced. In some embodiments, at least signal tap 250 or 252 isconfigured to limit a resistance between power or ground connections towells (shown in FIGS. 3A-3B) of substrate 202. In some embodiments, theuse of at least signal tap 250 or 252 results in less drift in substrate202 thereby preventing latch-up effects.

Signal tap 250 is coupled to the voltage supply node 104 (e.g., voltageVDD) on the backside 203 of substrate 202. Signal tap 250 is furthercoupled to the cathode of diode D1.

Signal tap 252 is coupled to the reference voltage supply node 106(e.g., voltage VSS) on the backside 203 of substrate 202. Signal tap 252is further coupled to the anode of diode D2.

IO pad 108 is on the backside 203 of substrate 202, and is coupled tothe anode of diode D1 and the cathode of diode D2. In some embodiments,integrated circuit 200 is electrically connected to one or more otherpackage structures (not shown) on the backside 203 of substrate 202.

In some embodiments, diode D1 is configured to share signal tap 250 withESD clamp circuit 220, and diode D2 is configured to share signal tap252 with ESD clamp circuit 220. In some embodiments, by sharing signaltap 250 with ESD clamp circuit 220, diode D1 does not include a signaltap resulting in integrated circuit 200 occupying less area than otherapproaches. In some embodiments, by sharing signal tap 252 with ESDclamp circuit 220, diode D2 does not include a signal tap resulting inintegrated circuit 200 occupying less area than other approaches.

By at least diode D1 or D2 not including corresponding signal taps,integrated circuit 200 has less resistance since integrated circuit 200includes fewer signal taps than other approaches.

Other types of clamp circuits, configurations and arrangements of ESDclamp circuit 120 are within the scope of the present disclosure.

Other configurations or quantities of circuits in integrated circuit 200are within the scope of the present disclosure.

FIG. 3A is a cross-sectional view of an integrated circuit 300A, inaccordance with some embodiments.

Integrated circuit 300A is an embodiment of at least integrated circuit100 of FIG. 1 or integrated circuit 200 of FIG. 2 , and similar detaileddescription is therefore omitted.

While FIGS. 3A-3B are described with respect to a portion of integratedcircuit 100 of FIG. 1 or integrated circuit 200 of FIG. 2 , theteachings of FIGS. 3A-3B are also applicable to other portions ofintegrated circuit 100 or 200 (not described with respect to at leastFIGS. 3A-3B), and similar detailed description is therefore omitted forbrevity.

Integrated circuit 300A includes a diode 302, a diode 304, an ESD clampcircuit 310 and a substrate 320.

Diode 302 is an embodiment of diode D1 of FIGS. 1-2 , diode 304 is anembodiment of diode D2 of FIGS. 1-2 , ESD clamp circuit 310 is anembodiment of ESD clamp circuit 120 of FIG. 1 or 210 of FIG. 2 , andsubstrate 320 is an embodiment of substrate 202 of FIG. 2 , and similardetailed description is therefore omitted.

At least diode 302, diode D2 or ESD clamp circuit 310 is formed onsubstrate 320. In some embodiments, at least diode 302, diode D2 or ESDclamp circuit 310 is formed on a front side 305 of substrate 320.

Substrate 320 has a front side 305 and a backside 303 opposite from thefront side 305 in a second direction Y. Substrate 320 has a side 326 anda side 336 opposite from side 326 in the first direction X. In someembodiments, a bulk of substrate 320 has been removed during waferthinning. In some embodiments, substrate 320 is part of a super powerrail (SPR) technology or process. In some embodiments, substrate 320 isa silicon on insulator (SOI) technology or process. In some embodiments,substrate 320 is also referred to as a wafer. In some embodiments,substrate 320 includes an insulating layer 321. Insulating layer 321 isbetween the back-side 303 and front-side 305 of substrate 320. In someembodiments, the insulating layer 321 is a non-conducting oxidematerial. In some embodiments, the insulating layer 321 is formed on theback-side 303 of substrate 320 after wafer thinning and oxide regrowth.In some embodiments, the front-side 305 and the back-side 303 areelectrically isolated from each other by at least the insulating layer321. In some embodiments, the insulating layer 321 includes a dielectricmaterial including oxide or another suitable insulating material.

Substrate 320 is a p-type substrate. In some embodiments, substrate 320is an n-type substrate. In some embodiments, substrate 320 includes anelemental semiconductor including silicon or germanium in crystal,polycrystalline, or an amorphous structure; a compound semiconductorincluding silicon carbide, gallium arsenic, gallium phosphide, indiumphosphide, indium arsenide, and indium antimonide; an alloysemiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GalnAs, GaInP, andGaInAsP; any other suitable material; or combinations thereof. In someembodiments, the alloy semiconductor substrate has a gradient SiGefeature in which the Si and Ge composition change from one ratio at onelocation to another ratio at another location of the gradient SiGefeature. In some embodiments, the alloy SiGe is formed over a siliconsubstrate. In some embodiments, substrate 320 is a strained SiGesubstrate. In some embodiments, the semiconductor substrate has asemiconductor on insulator structure, such as a silicon on insulator(SOI) structure. In some embodiments, the semiconductor substrateincludes a doped epi layer or a buried layer. In some embodiments, thecompound semiconductor substrate has a multilayer structure, or thesubstrate includes a multilayer compound semiconductor structure.

Diode 302 includes an anode 302 a, a gate structure 302 b, a cathode 302c, a cathode 302 d, a channel region 302 e and a well 322. Diode 302 isa vertical well diode. In some embodiments, diode 302 is a nanosheetvertical well diode. In some embodiments, diode 302 is formed on a frontside 305 of substrate 320. Other diode types for diode 302 are withinthe scope of the present disclosure.

Diode 302 corresponds to diode D1 of FIGS. 1-2 , and similar detaileddescription is omitted. Anode 302 a corresponds to the anode of diode D1of FIGS. 1-2 , cathodes 302 c and 302 d corresponds to the cathode ofdiode D1 of FIGS. 1-2 , and the channel region 302 e corresponds to achannel region of diode D1, and similar detailed description is omitted.

Well 322 is formed in substrate 320. Well 322 has p-type dopantimpurities and is referred to as a P-type well. In some embodiments,well 322 has n-type dopant impurities and is referred to as an N-typewell.

Well 322 includes a region 324. Region 324 is embedded in well 322.Region 324 is a heavily doped p-region. In some embodiments, region 324is a heavily doped n-region.

The anode 302 a includes well 322 and region 324. The anode 302 a is aP-type active region having P-type dopants in well 322.

The cathode 302 c is an N-type active region having N-type dopants andis located on well 322. The cathode 302 d is an N-type active regionhaving N-type dopants and is located on well 322. In some embodiments,at least cathode 302 c or 302 d is a P-type active region having P-typedopants. The cathode 302 c and the cathode 302 d are separated from eachother in the first direction X. In some embodiments, cathode 302 c andcathode 302 d are corresponding cathodes of two diodes coupled togetherin parallel. Integrated circuits 300A-300B are shown with two cathodes(e.g., cathodes 302 c and 302 d) and a single anode (e.g., anode 302 a).Other number of cathodes 302 c or 302 d and/or anodes 302 a are withinthe scope of the present disclosure.

The anode 302 a and the cathode 302 c together form a PN junction, andthe anode 302 a and the cathode 302 d together form another PN junction.In some embodiments, at least cathode 302 c or cathode 302 d extendsabove substrate 320. In some embodiments, at least a top surface ofcathode 302 c or a top surface of cathode 302 d is flush with the frontside 305 of substrate 320.

The gate structure 302 b is at least partially over well 322, and inbetween cathode 302 c and cathode 302 d. In some embodiments, the gatestructure 302 b is electrically floating. In some embodiments, the gatestructure 302 b is electrically coupled to cathodes 302 c and 302 d. Thechannel region 302 e couples the cathode 302 c and the cathode 302 d. Insome embodiments, the channel region 302 e is in well 322.

In some embodiments, diode 302 does not include a signal tap region. Insome embodiments, diode 302 is configured to share a signal tap region350 with ESD clamp circuit 310. For example, in some embodiments, diode302 is electrically coupled to the signal tap region 350 of ESD clampcircuit 310 by at least a conductive structure 390. In some embodiments,by sharing signal tap region 350 with ESD clamp circuit 310, integratedcircuit 300A or 300B occupies less area than other approaches. In someembodiments, by sharing signal tap region 350 with ESD clamp circuit310, integrated circuit 300A or 300B has less signal taps than otherapproaches resulting in integrated circuit 300A or 300B having lessresistance than other approaches, and simpler routing.

Other types of circuits, configurations and arrangements of diode 302are within the scope of the present disclosure.

Diode 304 includes an anode 304 a, a gate structure 304 b, a cathode 304c, a cathode 304 d, a channel region 304 e and a well 332. Diode 304 isa vertical well diode. In some embodiments, diode 304 is a nanosheetvertical well diode. In some embodiments, diode 304 is formed on a frontside 305 of substrate 320. Other diode types for diode 304 are withinthe scope of the present disclosure.

Diode 304 corresponds to diode D2 of FIGS. 1-2 , and similar detaileddescription is omitted. Anode 304 a corresponds to the anode of diode D2of FIGS. 1-2 , cathodes 304 c and 304 d corresponds to the cathode ofdiode D2 of FIGS. 1-2 , and the channel region 304 e corresponds to achannel region of diode D2, and similar detailed description is omitted.

Well 332 is formed in substrate 320. Well 332 has n-type dopantimpurities and is referred to as an N-type well. In some embodiments,well 332 has p-type dopant impurities and is referred to as a P-typewell.

Well 332 includes a region 334. Region 334 is embedded in well 332.Region 334 is a heavily doped n-region. In some embodiments, region 334is a heavily doped p-region.

The anode 304 a includes well 332 and region 334. The anode 304 a is anN-type active region having N-type dopants in well 332.

The cathode 304 c is a P-type active region having P-type dopants and islocated on well 332. The cathode 304 d is a P-type active region havingP-type dopants and is located on well 332. In some embodiments, at leastcathode 304 c or 304 d is an N-type active region having N-type dopants.The cathode 304 c and the cathode 304 d are separated from each other inthe first direction X. In some embodiments, cathode 304 c and cathode304 d are corresponding cathodes of two diodes coupled together inparallel. Integrated circuits 300A-300B are shown with two cathodes(e.g., cathodes 304 c and 304 d) and a single anode (e.g., anode 304 a).Other number of cathodes 304 c or 304 d and/or anodes 304 a are withinthe scope of the present disclosure.

The anode 304 a and the cathode 304 c together form a PN junction, andthe anode 304 a and the cathode 304 d together form another PN junction.In some embodiments, at least cathode 304 c or cathode 304 d extendsabove substrate 320. In some embodiments, at least a top surface ofcathode 304 c or a top surface of cathode 304 d is flush with the frontside 305 of substrate 320.

The gate structure 304 b is at least partially over well 332, and inbetween cathode 304 c and cathode 304 d. In some embodiments, the gatestructure 304 b is electrically floating. In some embodiments, the gatestructure 304 b is electrically coupled to cathodes 304 c and 304 d. Thechannel region 304 e couples the cathode 304 c and the cathode 304 d. Insome embodiments, the channel region 304 e is in well 332.

In some embodiments, diode 304 does not include a signal tap region. Insome embodiments, diode 304 is configured to share a signal tap region352 with ESD clamp circuit 310. For example, in some embodiments, diode304 is electrically coupled to the signal tap region 352 of ESD clampcircuit 310 by at least a conductive structure 392. In some embodiments,by sharing signal tap region 352 with ESD clamp circuit 310, integratedcircuit 300A or 300B occupies less area than other approaches. In someembodiments, by sharing signal tap region 352 with ESD clamp circuit310, integrated circuit 300A or 300B has less signal taps than otherapproaches resulting in integrated circuit 300A or 300B having lessresistance than other approaches, and simpler routing.

Other types of circuits, configurations and arrangements diode 304 arewithin the scope of the present disclosure.

ESD clamp circuit 310 includes an N-type Metal Oxide Semiconductor(NMOS) transistor N1, an NMOS transistor N2, signal tap region 250 andsignal tap region 252. NMOS transistor N1 is coupled in series with NMOStransistor N2. For ease of illustration, NMOS transistor N1 and NMOStransistor N2 are not shown as being coupled to other elements in FIGS.3A-3B. In some embodiments, at least NMOS transistor N1 or N2 is aP-type Metal Oxide Semiconductor (PMOS) transistor.

NMOS transistor N1 includes a drain region 310 a, a gate structure 310b, a source region 310 c, a channel region 310 d and a well region 360.

Well region 360 is formed in substrate 320. Well region 360 has p-typedopant impurities and is referred to as a P-type well. In someembodiments, well region 360 has n-type dopant impurities and isreferred to as an N-type well.

The gate structure 310 b is over well region 360. The drain region 310 ais an N-type active region having N-type dopants implanted in wellregion 360. The source region 310 c is an N-type active region havingN-type dopants implanted in well region 360. In some embodiments, atleast source region 310 c or drain region 310 a extends above substrate320. The channel region 310 d is in well region 360 and couples thedrain region 310 a and the source region 310 c.

NMOS transistor N2 includes a drain region 312 a, a gate structure 312b, a source region 312 c, a channel region 312 d and a well region 362.

Well region 362 is formed in substrate 320. Well region 362 has p-typedopant impurities and is referred to as a P-type well. In someembodiments, well region 362 has n-type dopant impurities and isreferred to as an N-type well.

The gate structure 312 b is over well region 362. The drain region 312 ais an N-type active region having N-type dopants implanted in wellregion 362. The source region 312 c is an N-type active region havingN-type dopants implanted in well region 362. In some embodiments, atleast source region 312 c or drain region 312 a extends above substrate320. The channel region 312 d is in well region 362 and couples thedrain region 312 a and the source region 312 c.

The signal tap region 350 is an embodiment of signal tap region 250 ofFIG. 2 , and the signal tap region 352 is an embodiment of signal tapregion 252 of FIG. 2 , and similar detailed description is thereforeomitted.

The signal tap region 350 is in well region 360. Signal tap region 350is coupled to a conductive structure 344. Each of signal tap region 350and conductive structure 344 are coupled to node Nd1 which correspondsto the voltage supply terminal (e.g., voltage VDD). Signal tap region350 is further coupled to cathode 302 c of diode D1 and cathode 302 d ofdiode D1 by a conductive line 390. In some embodiments, the signal tapregion 350 of ESD clamp circuit 310 is shared with diode 302.

In some embodiments, signal tap region 350 is a well tap, andelectrically couples well region 360 of substrate 320 to voltage supplynode 104 (e.g., supply voltage VDD). In some embodiments, the signal tapregion 350 includes a heavily doped n-region in well region 360 onsubstrate 320 (e.g., P-type). In some embodiments, the heavily dopedn-region is coupled through the well tap to voltage supply node 104(e.g., supply voltage VDD) thereby setting the potential of the wellregion 360 (e.g., N-type) to prevent leakage from adjacent source/drainregions into well region 360. In some embodiments, the signal tap region350 includes a heavily doped p-region in well region 360 on substrate320.

The signal tap region 352 is in well region 362. In some embodiments,well region 362 and 360 are part of a same continuous well. In someembodiments, well region 362 and 360 are separate discontinuous wells.Signal tap region 352 is coupled to a conductive structure 346. Each ofsignal tap region 352 and conductive structure 346 are coupled to nodeNd2 which corresponds to the reference voltage supply terminal (e.g.,voltage VSS). Signal tap region 352 is further coupled to cathode 304 cof diode D2 and cathode 304 d of diode D2 by a conductive line 392. Insome embodiments, signal tap region 352 of ESD clamp circuit 310 isshared with diode 304.

In some embodiments, signal tap region 352 is a substrate tap, andelectrically couples well region 362 of substrate 320 to referencevoltage supply node 106 (e.g., supply voltage VSS). In some embodiments,the signal tap region 352 includes a heavily doped p-region in wellregion 362 on substrate 320 (e.g., P-type). In some embodiments, theheavily doped p-region is coupled through the substrate tap to referencevoltage supply node 106 (e.g., supply voltage VSS) thereby setting thepotential of the substrate 320 (e.g., P-type) to prevent leakage fromadjacent source/drain regions. In some embodiments, the signal tapregion 352 includes a heavily doped n-region in well region 362 onsubstrate 320.

Each of the cathode 302 c of diode D1, the cathode 302 d of diode D1,and the signal tap region 350 are coupled together by conductive line390 that corresponds to node Nd1 of FIGS. 1-2 .

Each of the cathode 304 c of diode D2, the cathode 304 d of diode D2,and the signal tap region 352 are coupled together by conductive line392 that corresponds to node Nd2 of FIGS. 1-2 .

In some embodiments, the drain region 310 a and source region 310 c orthe drain region 312 a and source region 312 c of ESD clamp circuit 310of FIGS. 3A-3B is referred to as an oxide definition (OD) region whichdefines the source or drain diffusion regions of NMOS transistor N1 orN2 of FIGS. 3A-3B.

In some embodiments, at least drain region 310 a or 312 a is an extendeddrain region and has a greater size than at least source region 310 c or312 c. In at least one embodiment, a silicide layer (not shown) covers aportion, but not the entirety, of at least drain region 310 a or 312 a.Such a partially silicided configuration of drain region 310 a improvesself-protection of NMOS transistor N1 or N2 of ESD clamp circuit 310from ESD events. In at least one embodiment, at least drain region 310 aor 312 a is fully silicided.

Gate structure 310 b is arranged between drain region 310 a and sourceregion 310 c. Gate structure 312 b is arranged between drain region 312a and source region 312 c. In some embodiments, the gate structure 310 band gate structure 312 b are electrically coupled together.

In some embodiments, at least gate structure 302 b, 304 b, 310 b or 312b is a metal gate, and includes a conductive material such as a metal.In some embodiments, at least gate structure 302 b, 304 b, 310 b or 312b includes polysilicon (also referred to herein as “POLY”).

In some embodiments, at least channel region 302 e, 304 e, 310 d or 312d includes fins in accordance with fin field-effect transistor (FinFET)complementary metal-oxide-semiconductor (CMOS) technologies. In someembodiments, at least channel region 302 e, 304 e, 310 d or 312 dincludes nanosheets of nanosheet transistors. In some embodiments, atleast channel region 302 e, 304 e, 310 d or 312 d includes nanowire ofnanowire transistors. In some embodiments, at least channel region 302e, 304 e, 310 d or 312 d is free of fins in accordance with planar CMOStechnologies. Other types of transistors are within the scope of thepresent disclosure.

Other types of circuits, configurations and arrangements of ESD clampcircuit 310 are within the scope of the present disclosure.

Integrated circuit 300A further includes one or more shallow trenchisolation (STI) regions 328 a, 328 b, 328 c or 328 d.

STI region 328 a is adjacent to anode 304 a of diode 304. STI region 328b is between diode 302 and ESD clamp circuit 310. STI region 328 c isbetween diode 304 and ESD clamp circuit 310. STI region 328 d isadjacent to cathode 302 d of diode 302.

STI region 328 a is configured to electrically isolate portions of diode304 from other portions of integrated circuit 300A or 300B (not shown).STI region 328 b is configured to electrically isolate portions of diode304 and portions of ESD clamp circuit 310 from each other. In someembodiments, STI region 328 c is configured to electrically isolate atleast portions of diode 302 and portions of ESD clamp circuit 310 fromeach other. STI region 328 d is configured to electrically isolateportions of diode 302 from other portions of integrated circuit 300A or300B (not shown).

In some embodiments, at least STI region 328 a, 328 b, 328 c or 328 d isnot included in integrated circuit 300A or 300B. In some embodiments, inat least integrated circuit 300A or 300B, at least STI region 328 a, 328b, 328 c or 328 d is replaced with a corresponding dummy cell. In someembodiments, the dummy cell is a dummy device. In some embodiments, adummy device is a non-functional transistor or non-functional diodedevice.

In some embodiments, well region 322 and well region 360 are part of asame continuous well. In some embodiments, well region 322 and 360 areseparate discontinuous wells, and STI region 328 is positioned betweenthem.

In some embodiments, well region 332 and well region 362 are part of asame continuous well. In some embodiments, well region 322 and 362 areseparate discontinuous wells, and STI region 338 is positioned betweenthem.

In some embodiments, well region 360 is positioned between well region362 and well region 322. In some embodiments, well region 360 isadjacent to at least well region 362 or well region 322. In someembodiments, a first element is adjacent to a second element correspondsto the first element being directly next to the second element. In someembodiments, the first element is adjacent to the second elementcorresponds to the first element not being directly next to the secondelement. In some embodiments, diode 302 is adjacent to ESD clamp circuit310. In some embodiments, signal tap region 350 is adjacent to cathode302 c.

In some embodiments, well region 362 is positioned between well region360 and well region 332. In some embodiments, well region 362 isadjacent to at least well region 360 or well region 332. In someembodiments, diode 304 is adjacent to ESD clamp circuit 310. In someembodiments, signal tap region 352 is adjacent to cathode 304 c.

Other types of circuits, configurations and arrangements of ESD clampcircuit 310 are within the scope of the present disclosure.

Integrated circuit 300A further includes a conductive structure 340, aconductive structure 342, a conductive structure 344 and a conductivestructure 346. Conductive structure 340, conductive structure 342,conductive structure 344 and conductive structure 346 are formed on thebackside 203 of integrated circuits 300A-300B. In some embodiments, atleast conductive structure 340, conductive structure 342, conductivestructure 344 or conductive structure 346 is embedded in substrate 320.In some embodiments, at least conductive structure 340, conductivestructure 342, conductive structure 344 or conductive structure 346 isconfigured to provide an electrical connection between one or morecircuit elements of integrated circuit 300A-300B and other one or morecircuit elements of integrated circuit 300A-300B or other packagestructures (not shown).

In some embodiments, each of conductive structure 340, conductivestructure 342 and conductive structure 344 and conductive structure 346is a corresponding via. In some embodiments, one or more of conductivestructure 340, conductive structure 342 and conductive structure 344,conductive structure 346 or signal tap 350 are used to electricallycouple signals from the front-side 305 to the back-side 303 of substrate320 since the front-side 305 and the back-side 303 are electricallyisolated from each other by at least the insulating layer 321. In someembodiments, at least conductive structure 340, 342, 344 or 346 isdirectly coupled with corresponding source/drain region 310 a, 310 c or312 c.

In some embodiments, integrated circuit 300A is electrically connectedto one or more other package structures (not shown) on the backside 203of substrate 320 by at least conductive structure 340, conductivestructure 342, conductive structure 344 or conductive structure 346.

In some embodiments, at least conductive structure 340, conductivestructure 342, conductive structure 344 or conductive structure 346corresponds to a copper pillar structure that includes at least aconductive material such as copper, or the like.

In some embodiments, at least conductive structure 340, conductivestructure 342, conductive structure 344 or conductive structure 346corresponds to a solder bump structure that includes a conductivematerial having a low resistivity, such as solder or a solder alloy. Insome embodiments, a solder alloy includes Sn, Pb, Ag, Cu, Ni, Bi, orcombinations thereof. Other configurations, arrangements and materialsof at least conductive structure 340, conductive structure 342,conductive structure 344 or conductive structure 346 are within thecontemplated scope of the present disclosure.

Conductive structure 340 is coupled to the anode region 302 a of diode302. Conductive structure 340 is coupled to the well region 322 andregion 324 of diode 302. In some embodiments, conductive structure 340corresponds to node Nd3 of FIGS. 1-2 . In some embodiments, conductivestructure 340 is electrically coupled to node Nd3 of FIGS. 1-2 . In someembodiments, conductive structure 340 is electrically coupled to IO pad108 of FIGS. 1-2 .

Conductive structure 342 is coupled to the anode region 304 a of diode304. Conductive structure 342 is coupled to the well region 332 andregion 334 of diode 304. In some embodiments, conductive structure 342corresponds to node Nd3 of FIGS. 1-2 . In some embodiments, conductivestructure 342 is electrically coupled to node Nd3 of FIGS. 1-2 . In someembodiments, conductive structure 342 is electrically coupled to IO pad108 of FIGS. 1-2 .

In some embodiments, conductive structure 340 and conductive structure342 are coupled to each other. For ease of illustration, conductivestructure 340 and conductive structure 342 are not shown as beingcoupled to each other.

Conductive structure 344 is coupled to signal tap region 350. Conductivestructure 344 is configured to provide voltage VDD to signal tap region350. In some embodiments, conductive structure 344 is electricallycoupled to voltage supply node 104 (e.g., voltage VDD) of FIGS. 1-2 . Insome embodiments, conductive structure 344 corresponds to node Nd1 ofFIGS. 1-2 . In some embodiments, conductive structure 344 corresponds toa pad or a pin. In some embodiments, conductive structure 344 iselectrically coupled to node Nd1 of FIGS. 1-2 . In some embodiments,conductive structure 344 corresponds to node Nd1 of FIGS. 1-2 .

Conductive structure 346 is coupled to signal tap region 352. Conductivestructure 346 is configured to provide voltage VSS to signal tap region352. In some embodiments, conductive structure 346 is electricallycoupled to reference voltage supply node 106 (e.g., voltage VSS) ofFIGS. 1-2 . In some embodiments, conductive structure 346 corresponds tonode Nd2 of FIGS. 1-2 . In some embodiments, conductive structure 346corresponds to a pad or a pin. In some embodiments, conductive structure346 is electrically coupled to node Nd2 of FIGS. 1-2 . In someembodiments, conductive structure 346 corresponds to node Nd2 of FIGS.1-2 .

In some embodiments, at least conductive structure 340, 342, 344, 346,390 or 392 includes one or more layers of a conductive material. In someembodiments, the conductive material includes Tungsten, Cobalt,Ruthenium, Copper, or the like or combinations thereof.

Other configurations, arrangements and materials of at least conductivestructure 340, 342, 344, 346, 390 or 392 are within the contemplatedscope of the present disclosure.

Other configurations or quantities of circuits in integrated circuit300A are within the scope of the present disclosure.

During a PD mode of ESD stress or event, diode 302 is forward biased andcurrent I2 flows through diode 302 from the anode 302 a to the cathode302 c and cathode 302 d. Diode 302 is configured to transfer current I2or ESD voltage from IO pad 108 (node Nd3) to node Nd1. Current I2 flowsdirectly from cathode 302 c and cathode 302 d to signal tap region 350of ESD clamp circuit 302. In response to current I2 and ESD voltage atnode Nd1, NMOS transistors N1 and N2 in ESD clamp circuit 310 areconfigured to turn on, and discharge the ESD current I2 from signal tapregion 350 or node Nd1 through channel regions 310 d and 312 d to thereference voltage supply node 106 (e.g., VSS) by signal tap region 352and node Nd2.

In some embodiments, by sharing signal tap region 350 with ESD clampcircuit 310, integrated circuit 300A has less signal taps than otherapproaches, resulting in current I2 flowing through less signal tapsthan other approaches, and to flow directly from cathode 302 c andcathode 302 d to signal tap region 350 of ESD clamp circuit 320 therebyreducing the signal tap resistance of integrated circuit 300A comparedto other approaches.

FIG. 3B is a cross-sectional view of an integrated circuit 300B, inaccordance with some embodiments.

Integrated circuit 300B is an embodiment of at least ESD clamp circuit120 or 310, and similar detailed description is therefore omitted.Integrated circuit 300B is an embodiment of integrated circuit 300B, andsimilar detailed description is therefore omitted.

Integrated circuit 300B is an embodiment of at least integrated circuit100 of FIG. 1 or integrated circuit 200 of FIG. 2 , and similar detaileddescription is therefore omitted.

Integrated circuit 300B is a variation of integrated circuit 300A ofFIG. 3A, and similar detailed description is therefore omitted. Incomparison with integrated circuit 300A, current I1 replaces current I2,and similar detailed description is therefore omitted. In other words,integrated circuit 300B is configured to show ESD current flow during aPS mode of ESD stress.

During a PS mode of ESD stress or event, diode 304 is reverse biased andcurrent I1 flows through diode 304 from the anode 304 a to the cathode304 c and cathode 304 d. Diode 304 is configured to transfer current I1or ESD voltage from IO pad 108 (node Nd3) to node Nd2. Current I1 flowsdirectly from cathode 304 c and cathode 304 d to signal tap region 352of ESD clamp circuit 302. In response to current I1 and ESD voltage atnode Nd2, NMOS transistors N2 and N1 in ESD clamp circuit 310 areconfigured to turn on, and discharge the ESD current I1 from signal tapregion 352 or node Nd2 through channel regions 312 d and 310 d to thevoltage supply node 104 (e.g., VDD) by signal tap region 350 and nodeNd1.

In some embodiments, by sharing signal tap region 352 with ESD clampcircuit 310, integrated circuit 300B has less signal taps than otherapproaches, resulting in current I1 flowing through less signal tapsthan other approaches, and to flow directly from cathode 304 c andcathode 304 d to signal tap region 352 of ESD clamp circuit 320 therebyreducing the signal tap resistance of integrated circuit 300B comparedto other approaches.

Other configurations or quantities of circuits in integrated circuit300B are within the scope of the present disclosure.

FIG. 4 is a circuit diagram of an integrated circuit 400, in accordancewith some embodiments.

Integrated circuit 400 is an embodiment of at least ESD clamp circuit120 of FIG. 1 , and similar detailed description is therefore omitted.In some embodiments, integrated circuit 400 is an equivalent circuit forESD clamp circuit 310 of FIGS. 3A-3B. In some embodiments, NMOStransistor N1 of FIG. 4 corresponds to NMOS transistor N1 of FIGS.3A-3B, and NMOS transistor N2 of FIG. 4 corresponds to NMOS transistorN2 of FIGS. 3A-3B.

Integrated circuit 400 includes a resistor R1, a capacitor C1, aninverter I1, an NMOS transistor N1 and an NMOS transistor N2. In someembodiments, NMOS transistor N1 and NMOS transistor N2 are referred toas an ESD discharging circuit that is configured to couple node Nd1 andNd2 during an ESD event at node Nd1 or node Nd2, thereby providing anESD discharge path between node Nd1 and Nd2.

Each of a first end of resistor R1, node Nd1, a first voltage supplynode (not labelled) of inverter I1 and a drain of NMOS transistor N1 arecoupled together. Each of a second end of resistor R1, a first end ofcapacitor C1, an input terminal of inverter I1 and a node Nd4 arecoupled together.

Each of a second end of capacitor C1, node Nd2, a source of NMOStransistor N2, a body of NMOS transistor N1, a body of NMOS transistorN2 and a second voltage supply node (not labelled) of inverter I1 arecoupled together.

An output terminal of inverter I1 is coupled to a gate of NMOStransistor N1 and a gate of NMOS transistor N2.

In some embodiments, capacitor C1 is a transistor-coupled capacitor. Forexample in some embodiments, capacitor C1 is a transistor having a drainand source coupled together thereby forming a transistor-coupledcapacitor.

Resistor R1 and capacitor C1 are configured as an RC network. Dependentupon a location of an output of the RC network, the RC network isconfigured as either a low pass filter or a high pass filter.

In some embodiments, inverter I1 includes an NMOS transistor (not shown)and a PMOS transistor (not shown) coupled together as an invertercircuit. Thus, a slowly rising voltage at node Nd4 will be inverted byinverter I1 thereby causing node Nd3 to rapidly rise. Furthermore, arapidly rising voltage at node Nd4 will be inverted by inverter I1thereby causing node Nd3 to rise slowly. In some embodiments, inverterI1 is configured to generate an inverted input signal (not shown) inresponse to an input signal (not shown).

When an ESD event at node Nd1 occurs (e.g., ESD current I2 a in thereverse ESD direction), the ESD current or voltage at node Nd1 risesrapidly causing the voltage of node Nd4 (e.g., across capacitor C1) torise slowly (e.g., slower than rapidly) since the voltage at node Nd4corresponds to an output voltage of a low pass filter (e.g., a voltageacross capacitor C1 with respect to node Nd2). In other words, capacitorC1 is configured as a low pass filter, and the rapidly changing voltageor current from the ESD event is filtered by capacitor C1. In responseto the slowly rising voltage at node Nd4, a PMOS transistor (not shown)in inverter I1 will turn on thereby coupling node Nd3 to node Nd1 andcausing node Nd3 to rapidly rise from the ESD event at node Nd1. Thus,node Nd3 and the gate of NMOS transistors N1 and N2 are charged by theESD event at node Nd1. In response to being charged by the ESD event atnode Nd3, NMOS transistors N1 and N2 turn on and couple node Nd1 to nodeNd2. By being turned on and coupling node Nd1 to node Nd2, the channelsof NMOS transistors N1 and N2 discharge the ESD current I2 a in thereverse ESD direction from node Nd1 to Nd2.

When an ESD event at node Nd2 occurs (e.g., ESD current I1 a flows inthe forward ESD direction), the ESD current or voltage at node Nd2 risesrapidly, causing the voltage of node Nd4 (e.g., across capacitor C1) torise as well. However, a rising voltage at node Nd4 will be inverted byinverter I1 thereby causing node Nd3 to not rise from the ESD event atnode Nd2 causing NMOS transistors N1 and N2 to not turn on, and NMOStransistors N1 and N2 have a minimal effect on an ESD event at node Nd2.

Other configurations or quantities of circuits in integrated circuit 400are within the scope of the present disclosure.

FIG. 5 is a flowchart of a method 500 of operating an ESD circuit, inaccordance with some embodiments. In some embodiments, the circuit ofmethod 500 includes at least integrated circuit 100, 200 or 300A-300B(FIG. 1, 2 or 3A-3B). It is understood that additional operations may beperformed before, during, and/or after the method 500 depicted in FIG. 5, and that some other processes may only be briefly described herein. Itis understood that method 500 utilizes features of one or more ofintegrated circuit 100, 200 or 300A-300B.

Method 500 is applicable to at least integrated circuit 300A or 300B.Method 500 is initially described with respect to integrated circuit300A and current path I2. However, method 500 is also applicable tointegrated circuit 300B and current path I1, and is described belowafter the description of integrated circuit 300A. Other order ofoperations of method 500 to integrated circuit 300A or 300B is withinthe scope of the present disclosure.

At operation 502 of method 500, an ESD voltage of an ESD event isreceived on a first node. In some embodiments, the ESD voltage isgreater than a supply voltage VDD of a voltage supply. In someembodiments, the first node of method 500 includes node Nd3. In someembodiments, the first node of method 500 includes at least IO pad 108,conductive structure 340 or conductive structure 342.

At operation 504, a diode is turned on, thereby conducting an ESDcurrent from an anode of the diode to a cathode of the diode. In someembodiments, the diode of method 500 includes at least diode D1 or 302.In some embodiments, the anode of method 500 includes at least the anodeof diode D1 or anode 302 a. In some embodiments, the cathode of method500 includes at least the cathode of diode D1, cathode 302 c or 302 d.In some embodiments, the ESD current of method 500 includes current I2.

At operation 506, the ESD current is conducted from the cathode of thediode to a first signal tap of a clamp circuit. In some embodiments, thefirst signal tap of method 500 includes at least signal tap 250 or 350.In some embodiments, the clamp circuit of method 500 includes at leastESD clamp circuit 120, 220, or 310.

At operation 508, the ESD current of the ESD event is discharged by theESD clamp circuit. In some embodiments, the ESD current of the ESD eventis discharged by a channel of a first transistor or a channel of asecond transistor. In some embodiments, the first transistor of method500 includes NMOS transistor N1, and the channel includes channel region310 d. In some embodiments, the second transistor of method 500 includesNMOS transistor N2, and the channel includes channel region 312 d.

In some embodiments, operation 508 includes at least operation 510, 512,514 or 516.

At operation 510, the ESD clamp circuit is turned on in response to theESD current being received at the first signal tap of the ESD clampcircuit or a second node. In some embodiments, the second node of method500 includes node Nd1. In some embodiments, the second node of method500 corresponds to conductive structure 390.

At operation 512, the second node is coupled to a third node in responseto the ESD clamp circuit turning on. In some embodiments, the third nodeof method 500 includes node Nd2. In some embodiments, the third node ofmethod 500 corresponds to conductive structure 392. In some embodiments,the second node is coupled to the third node in response to the NMOStransistor N1 and NMOS transistor N2 of ESD clamp circuit turning on.

At operation 514, the ESD current is conducted from the first signal tapor the second node to a second signal tap of the ESD clamp circuit. Insome embodiments, the second signal tap of method 500 includes at leastsignal tap 252 or 352.

At operation 516, the ESD current is conducted from the second signaltap of the clamp circuit to a fourth node. In some embodiments, thefourth node of method 500 includes at least reference voltage supplynode 106 (e.g., voltage VSS) or conductive structure 346.

While method 500 was described with respect to integrated circuit 300Aand current path I2, method 500 is also applicable to integrated circuit300B and current path I1 and is described below with similar operations.

For example, at operation 502, the ESD voltage of the ESD event isreceived on the first node. In some embodiments, the ESD voltage isgreater than a reference supply voltage VSS of reference voltage supplynode 106. In some embodiments, the first node of method 500 includes atleast IO pad 108 or conductive structure 342.

At operation 504, the diode is turned on, thereby conducting the ESDcurrent from the anode of the diode to the cathode of the diode. In someembodiments, the diode of method 500 includes at least diode D2 or 304.In some embodiments, the anode of method 500 includes at least the anodeof diode D2 or anode 304 a. In some embodiments, the cathode of method500 includes at least the cathode of diode D2, cathode 304 c or 304 d.In some embodiments, the ESD current of method 500 includes current I1.

At operation 506, the ESD current is conducted from the cathode of thediode to the first signal tap of the clamp circuit. In some embodiments,the first signal tap of method 500 includes at least signal tap 252 or352.

At operation 508, the ESD current of the ESD event is discharged by theESD clamp circuit. In some embodiments, the SD current of the ESD eventis discharged by channel region 312 d of NMOS transistor N2 and channelregion 310 d of NMOS transistor N1.

At operation 510, the ESD clamp circuit is turned on in response to theESD current being received at the first signal tap of the ESD clampcircuit or the second node. In some embodiments, the second node ofmethod 500 includes node Nd2. In some embodiments, the second node ofmethod 500 corresponds to conductive structure 392.

At operation 512, the second node is coupled to the third node inresponse to the ESD clamp circuit turning on. In some embodiments, thethird node of method 500 includes node Nd1. In some embodiments, thethird node of method 500 corresponds to conductive structure 390. Insome embodiments, the second node is coupled to the third node inresponse to the NMOS transistor N1 and NMOS transistor N2 of ESD clampcircuit turning on.

At operation 514, the ESD current is conducted from the first signal tapor the second node to the second signal tap of the ESD clamp circuit. Insome embodiments, the second signal tap of method 500 includes at leastsignal tap 250 or 350.

At operation 516, the ESD current is conducted from the second signaltap of the clamp circuit to the fourth node. In some embodiments, thefourth node of method 500 includes at least voltage supply node 104(e.g., voltage VDD) or conductive structure 344.

In some embodiments, one or more of the operations of method 500 is notperformed. In some embodiments, one or more of the operations of method500 is repeated. In some embodiments, method 500 is repeated.

FIG. 6 is a flow chart of a method of manufacturing an integratedcircuit, in accordance with some embodiments. In some embodiments, themethod 600 is usable to manufacture or fabricate at least integratedcircuit 100, 200 or 300A-300B (FIG. 1, 2 or 3A-3B). It is understoodthat additional operations may be performed before, during, and/or afterthe method 600 depicted in FIG. 6 , and that some other processes mayonly be briefly described herein. It is understood that method 600utilizes features of one or more of integrated circuit 100, 200 or300A-300B.

Method 600 is applicable to at least integrated circuit 300A or 300B.Method 600 is described with respect to integrated circuit 300A.However, method 600 is also applicable to integrated circuit 300B. Otherorder of operations of method 600 to integrated circuit 300A or 300B iswithin the scope of the present disclosure.

In operation 602 of method 600, a first diode is fabricated on afront-side of a wafer. In some embodiments, the wafer of method 600includes substrate 320. In some embodiments, the front-side of the waferof method 600 includes at least front-side 305 of substrate 320. In someembodiments, the first diode of method 600 includes at least diode 302.

In some embodiments, operation 602 includes at least operation 602 a or602 b. In some embodiments, operation 602 a includes depositing an oxidelayer 704 (FIGS. 7A-7E) on the front-side 305 of substrate 320 and isshown in FIG. 7A.

In some embodiments, operation 602 b includes forming an opening in theoxide layer 704, and then filling the opening in the oxide layer with aconductive material thereby forming a via 706 (FIG. 7B), and growing anepitaxial layer 708 (FIG. 7B) in an unfilled portion of the opening andis shown in FIG. 7B. In some embodiments, the epitaxial layer 708 (FIG.7B) corresponds to cathode region 302 c and 302 d.

In some embodiments, operation 602 further includes fabricating well 322in substrate 320, fabricating a heavily doped region 324 in well 322thereby forming anode region 302 a of the first diode, fabricatingcathode region 302 c and 302 d in well 322, and fabricating gatestructure 302 b.

In some embodiments, at least well 322, well 360 or 362 (e.g., ESD clampcircuit 310) comprises p-type dopants. In some embodiments, thep-dopants include boron, aluminum or other suitable p-type dopants. Insome embodiments, at least well 322, well 360 or 362 comprises anepi-layer grown over substrate 320. In some embodiments, the epi-layeris doped by adding dopants during the epitaxial process. In someembodiments, the epi-layer is doped by ion implantation after theepi-layer is formed. In some embodiments, at least well 322, well 360 or362 is formed by doping substrate 320. In some embodiments, the dopingis performed by ion implantation. In some embodiments, at least well322, well 360 or 362 has a dopant concentration ranging from 1×10¹²atoms/cm³ to 1×10¹⁴ atoms/cm³. In some embodiments, region 324 is formedby a process similar to the formation of well 322. In some embodiments,region 324 is a heavily doped p-region.

In some embodiments, at least fabricating cathode regions 302 c and 302d of operation 602 or fabricating cathode regions 304 c and 304 d ofoperation 604 (described below) includes the formation of cathodefeatures in the substrate. In some embodiments, the formation of thecathode features includes removing a portion of the substrate to formrecesses at an edge of well 322 or 332, and a filling process is thenperformed by filling the recesses in the substrate. In some embodiments,the recesses are etched, for example, by a wet etching or a dry etching,after removal of a pad oxide layer or a sacrificial oxide layer. In someembodiments, the etch process is performed to remove a top surfaceportion of the active region adjacent to an isolation region, such asSTI region 328 a, 328 b, 328 c or 328 d. In some embodiments, thefilling process is performed by an epitaxy or epitaxial (epi) process.In some embodiments, the recesses are filled using a growth processwhich is concurrent with an etch process where a growth rate of thegrowth process is greater than an etch rate of the etch process. In someembodiments, the recesses are filled using a combination of growthprocess and etch process. For example, a layer of material is grown inthe recess and then the grown material is subjected to an etch processto remove a portion of the material. Then a subsequent growth process isperformed on the etched material until a desired thickness of thematerial in the recess is achieved. In some embodiments, the growthprocess continues until a top surface of the material is above the topsurface of the substrate. In some embodiments, the growth process iscontinued until the top surface of the material is co-planar with thetop surface of the substrate. In some embodiments, a portion of well 322or 332 is removed by an isotropic or an anisotropic etch process. Theetch process selectively etches well 322 or 332 without etching gatestructure 302 b or 304 b. In some embodiments, the etch process isperformed using a reactive ion etch (RIE), wet etching, or othersuitable techniques. In some embodiments, a semiconductor material isdeposited in the recesses to form the cathode features similar tosource/drain features. In some embodiments, an epi process is performedto deposit the semiconductor material in the recesses. In someembodiments, the epi process includes a selective epitaxy growth (SEG)process, CVD process, molecular beam epitaxy (MBE), other suitableprocesses, and/or combination thereof. The epi process uses gaseousand/or liquid precursors, which interacts with a composition ofsubstrate 320. In some embodiments, the cathode features includeepitaxially grown silicon (epi Si), silicon carbide, or silicongermanium. Cathode features of the IC device associated with gatestructure 302 b or 304 b are in-situ doped or undoped during the epiprocess in some instances. When cathode features are undoped during theepi process, cathode features are doped during a subsequent process insome instances. The subsequent doping process is achieved by an ionimplantation, plasma immersion ion implantation, gas and/or solid sourcediffusion, other suitable processes, and/or combination thereof. In someembodiments, cathode features are further exposed to annealing processesafter forming cathode features and/or after the subsequent dopingprocess.

In some embodiments, at least fabricating the gate regions of operation602, 604 or 606 (described below) includes performing one or moredeposition processes to form one or more dielectric material layers. Insome embodiments, a deposition process includes a chemical vapordeposition (CVD), a plasma enhanced CVD (PECVD), an atomic layerdeposition (ALD), or other process suitable for depositing one or morematerial layers. In some embodiments, fabricating the gate regionsincludes performing one or more deposition processes to form one or moreconductive material layers. In some embodiments, fabricating the gateregions includes forming gate electrodes or dummy gate electrodes. Insome embodiments, fabricating the gate regions includes depositing orgrowing at least one dielectric layer, e.g., gate dielectric. In someembodiments, gate regions are formed using a doped or non-dopedpolycrystalline silicon (or polysilicon). In some embodiments, the gateregions include a metal, such as Al, Cu, W, Ti, Ta, TiN, TaN, NiSi,CoSi, other suitable conductive materials, or combinations thereof.

In operation 604 of method 600, a second diode is fabricated on thefront-side of the wafer. In some embodiments, the back-side of the waferof method 600 includes at least back-side 303 of substrate 320. In someembodiments, the second diode of method 600 includes at least diode 304.

In some embodiments, operation 604 includes at least operation 604 a or604 b. In some embodiments, operation 604 a includes depositing oxidelayer 704 (FIGS. 7A-7E) on the front-side 305 of substrate 320 and isshown in FIG. 7A.

In some embodiments, operation 604 b includes forming an opening in theoxide layer 704, and then filling the opening in the oxide layer with aconductive material thereby forming a via 706 (FIG. 7B), and growing anepitaxial layer 708 (FIG. 7B) is grown in an unfilled portion of theopening and is shown in FIG. 7B. In some embodiments, the epitaxiallayer 708 (FIG. 7B) corresponds to cathode region 304 c and 304 d.

In some embodiments, operation 604 further includes fabricating well 332in substrate 320, fabricating a heavily doped region 334 in well 332thereby forming anode region 304 a of the second diode, fabricatingcathode region 304 c and 304 d above well 332, and fabricating gatestructure 304 b.

In some embodiments, well 332 comprises n-type dopants. In someembodiments, the n-type dopants include phosphorus, arsenic or othersuitable n-type dopants. In some embodiments, the n-type dopantconcentration ranges from about 1×10¹² atoms/cm³ to about 1×10¹⁴atoms/cm³. In some embodiments, well 332 is formed by ion implantation.The power of the ion implantation ranges from about 1500 k electronvolts (eV) to about 8000 k eV. In some embodiments, well 332 isepitaxially grown. In some embodiments, well 332 comprises an epi-layergrown over the surface. In some embodiments, the epi-layer is doped byadding dopants during the epitaxial process. In some embodiments, theepi-layer is doped by ion implantation after the epi-layer is formed,and has the dopant concentration described above. In some embodiments,region 334 is formed by a process similar to the formation of well 332.In some embodiments, region 334 is a heavily doped n-region.

In operation 606 of method 600, an ESD clamp circuit is fabricated onthe front-side of the wafer. In some embodiments, the ESD clamp circuitof method 600 includes at least ESD clamp circuit 310.

In some embodiments, operation 606 includes at least operation 606 a or606 b. In some embodiments, operation 606 a includes depositing oxidelayer 704 (FIGS. 7A-7E) on the front-side 305 of substrate 320 and isshown in FIG. 7A.

In some embodiments, operation 606 b includes forming an opening in theoxide layer 704, and then filling the opening in the oxide layer with aconductive material thereby forming a via 706 (FIG. 7B), and growing anepitaxial layer 708 (FIG. 7B) in an unfilled portion of the opening andis shown in FIG. 7B. In some embodiments, the epitaxial layer 708 (FIG.7B) corresponds to source 310 c or 312 c and drain 310 a or 312 a.

In some embodiments, operation 606 further includes fabricating wells360 and 362 in substrate 320, fabricating source/drain regions (e.g.,source 310 c and drain 310 a) in well 360, and fabricating source/drainregions (e.g., source 312 c and drain 312 a) in well 362, andfabricating gate structures 310 b and 312 b.

In some embodiments, fabricating source/drain regions (e.g., source 310c and drain 310 a) in well 360 of operation 606 includes operation 608.In some embodiments, fabricating source/drain regions (e.g., source 312c and drain 312 a) in well 362 of operation 606, and fabricating gatestructures 310 b and 312 b includes operation 610.

In operation 608 of method 600, a first signal tap region is fabricatedon the front-side of the wafer. In some embodiments, the first signaltap region of method 600 includes at least signal tap region 350. Insome embodiments, signal tap region 350 corresponds to drain 310 a ofESD clamp circuit 310. In some embodiments, operation 608 corresponds tooperation 606 b.

In operation 610 of method 600, a second signal tap is fabricated on thefront-side of the wafer. In some embodiments, the second signal tapregion of method 600 includes at least signal tap region 352. In someembodiments, signal tap region 352 corresponds to source 312 c of ESDclamp circuit 310. In some embodiments, operation 608 corresponds tooperation 606 b.

In some embodiments, at least signal tap region 350 or 352 comprisesp-type dopants. In some embodiments, the p-dopants include boron,aluminum or other suitable p-type dopants. In some embodiments, at leastsignal tap region 350 or 352 is formed by a process similar to theformation of corresponding well 360 or 362. In some embodiments, atleast signal tap region 350 or 352 is a heavily doped p-region.

In some embodiments, at least signal tap region 350 or 352 comprisesn-type dopants. In some embodiments, the n-type dopants includephosphorus, arsenic or other suitable n-type dopants. In someembodiments, the n-type dopant concentration ranges from about 1×10¹²atoms/cm2 to about 1×10¹⁴ atoms/cm2. In some embodiments, at leastsignal tap region 350 or 352 is formed by ion implantation. The power ofthe ion implantation ranges from about 1500 k electron volts (eV) toabout 8000 k eV. In some embodiments, at least signal tap region 350 or352 is a heavily doped n-region.

In some embodiments, at least signal tap region 350 or 352 isepitaxially grown. In some embodiments, at least signal tap region 350or 352 comprises an epi-layer grown over substrate 320. In someembodiments, the epi-layer is doped by adding dopants during theepitaxial process. In some embodiments, the epi-layer is doped by ionimplantation after the epi-layer is formed. In some embodiments, atleast signal tap region 350 or 352 is formed by doping substrate 320. Insome embodiments, the doping is performed by ion implantation. In someembodiments, at least signal tap region 350 or 352 has a dopantconcentration ranging from 1×10¹² atoms/cm3 to 1×10¹⁴ atoms/cm3.

In operation 612 of method 600, a first set of conductive structures 710(FIG. 7C) is fabricated on the front-side 305 of the wafer 320. FIG. 7Cis a cross-sectional view of the first set of conductive structures 710fabricated on the front-side 305 of the wafer 320 following at leastoperation 612, in accordance with one or more embodiments.

In some embodiments, operation 612 includes depositing the first set ofconductive structures 710 on the front-side 305 of the wafer 320. Insome embodiments, the first set of conductive structures 710 of method600 includes at least conductive structure 390 and conductive structure392.

In some embodiments, operation 612 includes depositing an insulatinglayer 712 (FIG. 7C) on the front-side 305 of the wafer 320, removingportions of the insulating layer 712 from the front-side 305 of thewafer 320, and depositing the first set of conductive structures 710 inthe removed portions of the insulating layer 712 on the front-side 305of the wafer 320. In some embodiments, the first set of conductivestructures of method 600 are formed using a combination ofphotolithography and material removal processes to form openings in aninsulating layer (not shown) over the substrate. In some embodiments,the photolithography process includes patterning a photoresist, such asa positive photoresist or a negative photoresist. In some embodiments,the photolithography process includes forming a hard mask, anantireflective structure, or another suitable photolithographystructure. In some embodiments, the material removal process includes awet etching process, a dry etching process, an RIE process, laserdrilling or another suitable etching process. The openings are thenfilled with conductive material, e.g., copper, aluminum, titanium,nickel, tungsten, or other suitable conductive material. In someembodiments, the openings are filled using CVD, PVD, sputtering, ALD orother suitable formation process.

In operation 614 of method 600, wafer thinning is performed on theback-side 303 of the wafer. FIG. 7D is a cross-sectional view of thewafer 320 prior to the wafer thinning of operation 614, in accordancewith one or more embodiments.

In some embodiments, operation 614 includes flipping the wafer 320 over,and performing a thinning process on the back-side 303 of thesemiconductor wafer or substrate. In some embodiments, the thinningprocess includes a grinding operation and a polishing operation (such aschemical mechanical polishing (CMP)) or other suitable processes. Insome embodiments, after the thinning process, a wet etching operation isperformed to remove defects formed on the backside 303 of thesemiconductor wafer 320 or substrate.

In operation 616 of method 600, an insulating layer 722 (FIG. 7E) isdeposited on the back-side of the wafer. In some embodiments, theinsulating layer 722 of method 600 includes insulating layer 321. Insome embodiments, the insulating layer 321 includes a dielectricmaterial including oxide or another suitable insulating material. Insome embodiments, the insulating layer 321 is formed by CVD, spin-onpolymeric dielectric, atomic layer deposition (ALD), or other processes.

In operation 618 of method 600, portions of the insulating layer 722 areremoved from the back-side of the wafer. In some embodiments, operation618 of method 600 uses a combination of photolithography and materialremoval processes to form openings in an insulating layer 722 over thewafer 320. In some embodiments, the photolithography process includespatterning a photoresist, such as a positive photoresist or a negativephotoresist. In some embodiments, the photolithography process includesforming a hard mask, an antireflective structure, or another suitablephotolithography structure. In some embodiments, the material removalprocess includes a wet etching process, a dry etching process, an RIEprocess, laser drilling or another suitable etching process.

In operation 620 of method 600, a second set of conductive structures720 (FIG. 7E) is deposited in at least the removed portion of theinsulating layer. FIG. 7E is a cross-sectional view of the wafer 320following at least operation 620, in accordance with one or moreembodiments.

In some embodiments, operation 620 includes depositing the second set ofconductive structures 720 on the back-side of the wafer. In someembodiments, the second set of conductive structures 720 of method 600includes at least conductive structure 340, conductive structure 342,conductive structure 344 or conductive structure 346.

In some embodiments, operation 620 includes filling the openings in theinsulating layer 722 with conductive material, e.g., copper, aluminum,titanium, nickel, tungsten, or other suitable conductive material. Insome embodiments, the openings are filled using CVD, PVD, sputtering,ALD or other suitable formation process.

In some embodiments, one or more of the operations of method 600 is notperformed. In some embodiments, one or more of the operations of method600 is repeated. In some embodiments, method 600 is repeated.

FIGS. 7A-7E are cross-sectional views of an integrated circuit, inaccordance with one or more embodiments.

FIG. 7A is a cross-sectional view of an integrated circuit 700A, inaccordance with one or more embodiments. In some embodiments, integratedcircuit 700A corresponds to an integrated circuit, such as integratedcircuit 300A or 300B, following at least operation 602 a, 604 a or 606a. In some embodiments, integrated circuit 700A includes an oxide layer704 on substrate 320.

FIG. 7B is a cross-sectional view of an integrated circuit 700B, inaccordance with one or more embodiments. In some embodiments, integratedcircuit 700B corresponds to an integrated circuit, such as integratedcircuit 300A or 300B, following at least operation 602 b, 604 b or 606b. In some embodiments, integrated circuit 700B includes via 706 formedin an opening of at least the oxide layer 704 or the substrate 320. Insome embodiments, integrated circuit 700B further includes an epitaxiallayer 708 over via 706, the oxide layer 704 and the substrate 320. Insome embodiments, the epitaxial layer 708 is grown in an unfilledportion of the opening of the oxide layer 704.

FIG. 7C is a cross-sectional view of an integrated circuit 700C, inaccordance with one or more embodiments. In some embodiments, integratedcircuit 700C corresponds to an integrated circuit, such as integratedcircuit 300A or 300B, following at least operation 612. In someembodiments, integrated circuit 700C includes the first set ofconductive structures 710, insulating layer 712 and integrated circuit700B. In some embodiments, integrated circuit 700C includes the firstset of conductive structures 710 fabricated in removed portions ofinsulating layer 712 on the front-side 305 of the wafer 320.

FIG. 7D is a cross-sectional view of an integrated circuit 700D, inaccordance with one or more embodiments. In some embodiments, integratedcircuit 700D corresponds to an integrated circuit, such as integratedcircuit 300A or 300B, prior to the wafer thinning of operation 614. Insome embodiments, integrated circuit 700D includes integrated circuit700C flipped over.

FIG. 7E is a cross-sectional view of an integrated circuit 700E, inaccordance with one or more embodiments. In some embodiments, integratedcircuit 700E corresponds to an integrated circuit, such as integratedcircuit 300A or 300B, following at least operation 620. In someembodiments, integrated circuit 700E includes the second set ofconductive structures 720, insulating layer 722 and integrated circuit700D (without the removed portion of wafer 320). In some embodiments,integrated circuit 700E includes the second set of conductive structures720 fabricated in removed portions of insulating layer 722 of the wafer320.

Other diode types or numbers of diodes, or other transistor types orother numbers of transistors in at least integrated circuit 100, 200 and300A-300B of corresponding FIGS. 1, 2 and 3A-3B are within the scope ofthe present disclosure.

Furthermore, various NMOS or PMOS transistors shown in FIGS. 3A-3B areof a particular dopant type (e.g., N-type or P-type) and are forillustration purposes. Embodiments of the disclosure are not limited toa particular transistor type, and one or more of the PMOS or NMOStransistors shown in FIGS. 3A-3B can be substituted with a correspondingtransistor of a different transistor/dopant type. Similarly, the low orhigh logical value of various signals used in the above description isalso used for illustration. Embodiments of the disclosure are notlimited to a particular logical value when a signal is activated and/ordeactivated. Selecting different logical values is within the scope ofvarious embodiments. Selecting different numbers of PMOS transistors in3A-3B is within the scope of various embodiments.

One aspect of this description relates to an ESD protection circuit. TheESD protection circuit includes a first diode, a second diode and an ESDclamp circuit. The first diode is in a semiconductor wafer, and iscoupled to an IO pad. The second diode is in the semiconductor wafer,and is coupled to the first diode and the IO pad. The ESD clamp circuitis in the semiconductor wafer, and is coupled to the first diode and thesecond diode. The ESD clamp circuit includes a first signal tap regionin the semiconductor wafer. The first signal tap region is coupled to afirst voltage supply. The first diode is coupled to and configured toshare the first signal tap region with the ESD clamp circuit.

Another aspect of this description relates to an ESD protection circuit.The ESD protection circuit includes a first diode, a second diode, aninternal circuit and an ESD clamp circuit. The first diode is in asemiconductor wafer, and is coupled to a first pad. The second diode isin the semiconductor wafer, and is coupled to the first diode and thefirst pad. The internal circuit is coupled to the first diode and thesecond diode The ESD clamp circuit is in the semiconductor wafer, iscoupled to the first diode by a first node and is coupled to the seconddiode by a second node. The ESD clamp circuit includes a first signaltap region coupled to a voltage supply, and a second signal tap regioncoupled to a reference voltage supply. The first diode is coupled to andconfigured to share the first signal tap region with the ESD clampcircuit. The second diode is coupled to and configured to share thesecond signal tap region with the ESD clamp circuit.

Yet another aspect of this description relates to a method of operatingan ESD protection circuit. The method includes receiving a first ESDvoltage on a first node, the first ESD voltage being greater than asupply voltage of a voltage supply, the first ESD voltage correspondingto a first ESD event. The method further includes turning on a firstdiode, thereby conducting a first ESD current from a first anode of thefirst diode to a first cathode of the first diode. The method furtherincludes conducting the first ESD current from the first cathode of thefirst diode to a first signal tap of an ESD clamp circuit. The methodfurther includes discharging the first ESD current of the first ESDevent by the ESD clamp circuit.

A number of embodiments have been described. It will nevertheless beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. For example, various transistorsbeing shown as a particular dopant type (e.g., N-type or P-type MetalOxide Semiconductor (NMOS or PMOS)) are for illustration purposes.Embodiments of the disclosure are not limited to a particular type.Selecting different dopant types for a particular transistor is withinthe scope of various embodiments. The low or high logical value ofvarious signals used in the above description is also for illustration.Various embodiments are not limited to a particular logical value when asignal is activated and/or deactivated. Selecting different logicalvalues is within the scope of various embodiments. In variousembodiments, a transistor functions as a switch. A switching circuitused in place of a transistor is within the scope of variousembodiments. In various embodiments, a source of a transistor can beconfigured as a drain, and a drain can be configured as a source. Assuch, the term source and drain are used interchangeably. Varioussignals are generated by corresponding circuits, but, for simplicity,the circuits are not shown.

Various figures show capacitive circuits using discrete capacitors forillustration. Equivalent circuitry may be used. For example, acapacitive device, circuitry or network (e.g., a combination ofcapacitors, capacitive elements, devices, circuitry, or the like) can beused in place of the discrete capacitor. The above illustrations includeexemplary steps, but the steps are not necessarily performed in theorder shown. Steps may be added, replaced, changed order, and/oreliminated as appropriate, in accordance with the spirit and scope ofdisclosed embodiments.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An electrostatic discharge (ESD) protectioncircuit, comprising: a first diode in a semiconductor wafer, and beingcoupled to an input output (IO) pad; a second diode in the semiconductorwafer, and being coupled to the first diode and the IO pad; and an ESDclamp circuit in the semiconductor wafer, coupled to the first diode andthe second diode, the ESD clamp circuit including a first signal tapregion in the semiconductor wafer, the first signal tap region beingcoupled to a first voltage supply, the first diode being coupled to andconfigured to share the first signal tap region with the ESD clampcircuit.
 2. The ESD protection circuit of claim 1, wherein the ESD clampcircuit further includes a second signal tap region in the semiconductorwafer, the second signal tap region being coupled to a second voltagesupply different from the first voltage supply, the second diode beingcoupled to and configured to share the second signal tap region with theESD clamp circuit.
 3. The ESD protection circuit of claim 2, furthercomprising: a first conductive structure coupled between the firstvoltage supply and the first signal tap region; and a second conductivestructure coupled between the second voltage supply and the secondsignal tap region, the first conductive structure and the secondconductive structure are located on a backside of the semiconductorwafer.
 4. The ESD protection circuit of claim 3, wherein the firstconductive structure is configured to provide a first voltage of thefirst voltage supply to the first signal tap region; and the secondconductive structure is configured to provide a second voltage of thesecond voltage supply to the second signal tap region.
 5. The ESDprotection circuit of claim 1, further comprising: an IO circuit in thesemiconductor wafer, being coupled to the first diode, the second diode,and the IO pad.
 6. The ESD protection circuit of claim 1, wherein the IOpad comprises: a first conductive structure coupled to a first anode ofthe first diode; and a second conductive structure coupled to a secondanode of the second diode, the first conductive structure and the secondconductive structure are located on a backside of the semiconductorwafer.
 7. The ESD protection circuit of claim 1, wherein at least thefirst diode or the second diode does not have a signal tap region. 8.The ESD protection circuit of claim 1, wherein the first diode is afirst nanosheet vertical well diode; the second diode is a secondnanosheet vertical well diode; and the ESD clamp circuit is at least onenanosheet transistor device.
 9. An electrostatic discharge (ESD)protection circuit, comprising: a first diode in a semiconductor wafer,and being coupled to a first pad; a second diode in the semiconductorwafer, and being coupled to the first diode and the first pad; aninternal circuit coupled to the first diode and the second diode; and anESD clamp circuit in the semiconductor wafer, coupled to the first diodeby a first node and coupled to the second diode by a second node, theESD clamp circuit including a first signal tap region coupled to avoltage supply, and a second signal tap region coupled to a referencevoltage supply, wherein the first diode is coupled to and configured toshare the first signal tap region with the ESD clamp circuit; and thesecond diode is coupled to and configured to share the second signal tapregion with the ESD clamp circuit.
 10. The ESD protection circuit ofclaim 9, wherein the first diode comprises: a first anode in thesemiconductor wafer; and a first cathode in the semiconductor wafer,being above the first anode and being coupled to the first signal tapregion by the first node.
 11. The ESD protection circuit of claim 10,wherein the first diode further comprises: a second cathode in thesemiconductor wafer, being above the first anode and being coupled tothe first signal tap region and the first cathode by the first node. 12.The ESD protection circuit of claim 11, wherein the second diodecomprises: a second anode in the semiconductor wafer; and a thirdcathode in the semiconductor wafer, being above the second anode andbeing coupled to the second signal tap region by the second node. 13.The ESD protection circuit of claim 12, wherein the second diode furthercomprises: a fourth cathode in the semiconductor wafer, being above thesecond anode and being coupled to the second signal tap region and thethird cathode by the second node.
 14. The ESD protection circuit ofclaim 13, further comprising: a first conductive structure coupledbetween the voltage supply and the first signal tap region; and a secondconductive structure coupled between the reference voltage supply andthe second signal tap region, the first conductive structure and thesecond conductive structure are located on a backside of thesemiconductor wafer.
 15. The ESD protection circuit of claim 14, whereinthe first pad comprises: a third conductive structure coupled to thefirst anode of the first diode; a fourth conductive structure coupled tothe second anode of the second diode, the third conductive structure andthe fourth conductive structure are located on the backside of thesemiconductor wafer.
 16. The ESD protection circuit of claim 9, whereinthe ESD clamp circuit is coupled between the first diode and the seconddiode.
 17. A method of operating an electrostatic discharge (ESD)protection circuit, the method comprising: receiving a first ESD voltageon a first node, the first ESD voltage being greater than a supplyvoltage of a voltage supply, the first ESD voltage corresponding to afirst ESD event; turning on a first diode, thereby conducting a firstESD current from a first anode of the first diode to a first cathode ofthe first diode; conducting the first ESD current from the first cathodeof the first diode to a first signal tap of an ESD clamp circuit,wherein the ESD clamp circuit is coupled to the first diode, the firstsignal tap is coupled to the voltage supply, and the first diode iscoupled to and configured to share the first signal tap with the ESDclamp circuit; and discharging the first ESD current of the first ESDevent by the ESD clamp circuit.
 18. The method of claim 17, whereindischarging the first ESD current of the first ESD event by the ESDclamp circuit comprises: turning on the ESD clamp circuit in response tothe first ESD current being received at the first signal tap of the ESDclamp circuit or a second node; coupling the second node to a third nodein response to the ESD clamp circuit turning on; conducting the firstESD current from the first signal tap to a second signal tap of the ESDclamp circuit; and conducting the first ESD current from the secondsignal tap of the ESD clamp circuit to a fourth node.
 19. The method ofclaim 18, further comprising: receiving a second ESD voltage on thefirst node, the second ESD voltage being greater than a reference supplyvoltage of a reference voltage supply, the second ESD voltagecorresponding to a second ESD event; turning on a second diode, therebyconducting a second ESD current from a second anode of the second diodeto a second cathode of the second diode; conducting the second ESDcurrent from the second cathode of the second diode to the second signaltap of the ESD clamp circuit; and discharging the second ESD current ofthe second ESD event by the ESD clamp circuit.
 20. The method of claim19, wherein discharging the second ESD current of the second ESD eventby the ESD clamp circuit comprises: turning on the ESD clamp circuit inresponse to the second ESD current being received at the second signaltap of the ESD clamp circuit or the third node; coupling the third nodeto the second node in response to the ESD clamp circuit turning on;conducting the second ESD current from the second signal tap to thefirst signal tap of the ESD clamp circuit; and conducting the second ESDcurrent from the first signal tap of the ESD clamp circuit to a fifthnode.